Move Declarative Web Request API out of experimental and make it a feature

chrome/common/extensions/docs/examples/api/transientPage/basic/background.js

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Global variables only exist for the life of the page, so they get reset
 // each time the page is unloaded.
 var counter = 1;
 
 var lastTabId = -1;
 function sendMessage() {
   chrome.tabs.query({active: true, currentWindow: true}, function(tabs) {
     lastTabId = tabs[0].id;
     chrome.tabs.sendMessage(lastTabId, "Background page started.");
   });
 }
 
 sendMessage();
 chrome.browserAction.setBadgeText({text: "ON"});
 console.log("Loaded.");
 
 chrome.experimental.runtime.onInstalled.addListener(function() {
   console.log("Installed.");
 
   // localStorage is persisted, so it's a good place to keep state that you
   // need to persist across page reloads.
   localStorage.counter = 1;
 
   // Register a webRequest rule to redirect bing to google.
-  var wr = chrome.experimental.webRequest;
-  chrome.experimental.webRequest.onRequest.addRules([{
+  var wr = chrome.declarativeWebRequest;
+  chrome.declarativeWebRequest.onRequest.addRules([{
     id: "0",
     conditions: [new wr.RequestMatcher({url: {hostSuffix: "bing.com"}})],
     actions: [new wr.RedirectRequest({redirectUrl: "http://google.com"})]
   }]);
 });
 
 chrome.bookmarks.onRemoved.addListener(function(id, info) {
   alert("I never liked that site anyway.");
 });
 
@@ skipping 40 matching lines @@
     function() {
   chrome.tabs.query({active: true, currentWindow: true}, function(tabs) {
     // After the unload event listener runs, the page will unload, so any
     // asynchronous callbacks will not fire.
     alert("This does not show up.");
   });
   console.log("Unloading.");
   chrome.browserAction.setBadgeText({text: ""});
   chrome.tabs.sendMessage(lastTabId, "Background page unloaded.");
 });